Use of a Cationic Silicon Dioxide Dispersion as a Textile Finishing Agent

ABSTRACT

An aqueous dispersion for use as a finishing agent for textiles, wherein the dispersion contains a pyrogenically produced, aggregated silicon dioxide powder and a cationic polymer which is soluble in the dispersion, wherein the cationic polymer is present in a quantity such that the particles of the silicon dioxide powder exhibit a positive zeta potential.

The invention relates to a cationic silicon dioxide dispersion for useas a textile finishing agent.

It has long been known to use silica as an non-slip agent for textiles(Ullmann's Encyclopedia of Industrial Chemistry, Vol. A26, p. 328, 5thedition). These silica sols may have specific surface areas of more than1000 m²/g. They generally assume the form of isolated, sphericalparticles with diameters of a few nanometres. In order to preventgelation, they are generally stabilised by the addition of aluminiumsalts or polymers. In the case of use as an non-slip agent, it hasproved disadvantageous that, in order to achieve the desired effect ofslip resistance, it is sometimes necessary to use large quantities ofsilica sol or cationised silica sol. This is possibly due to thespherical structure of the silica sol particles. Better results may beobtained with partially aggregated silica sol particles, as described inWO 2004/007367. The low degree of aggregation of the silica solparticles is disadvantageous here. Furthermore, the bond between thesilica sol particles is not so strong that the energy introduced in theevent of any external force applied to the particles is sufficient toseparate the aggregates again.

The object of the present invention is to provide a dispersioncontaining silicon dioxide which may be used as a textile finishingagent and avoids the disadvantages of the prior art.

The present invention provides an aqueous dispersion for use as afinishing agent for textiles, wherein the dispersion contains apyrogenically produced, aggregated silicon dioxide powder and a cationicpolymer which is soluble in the dispersion, wherein the cationic polymeris present in a quantity such that the particles of the silicon dioxidepowder exhibit a positive zeta potential.

Pyrogenically produced silicon dioxide powders should be taken to meanthose which are obtainable by flame hydrolysis or flame oxidation. Inthese processes, primary particles of approx. 5 to 50 nm are initiallyformed, which, as the reaction proceeds, combine to form aggregates.These aggregates form a three-dimensional network. The aggregates cannotgenerally be broken back down into the primary particles.

The specific surface area of the pyrogenically produced silicon dioxidepowder in the aqueous dispersion is not limited. It may preferably havea specific surface area of 50 to 300 m²/g.

A preferred dispersion may be one in which the pyrogenically producedsilicon dioxide powder is doped with up to 1 wt. % of aluminium oxide orpotassium. Such powders are described, for example, in EP-A-995718 andEP-A-1216956.

The content of pyrogenically produced silicon dioxide powder in thedispersion may preferably amount to 3 to 50 wt. %.

Selection of the cationic polymer is not limited according to thepresent invention, but the quantity thereof is. The cationic polymersmust be present in the dispersion in a quantity such that the surface ofthe particles of the silicon dioxide powder is completely covered withcationic polymer and consequently exhibits a positive zeta potential.

The content of cationic polymer is preferably between 0.1 and 15 wt. %and particularly preferably between 0.8 and 5 wt. %, relative to thequantity of cationic polymer and silicon dioxide powder.

Cationic polymers with a molecular weight of less than 100 000 g/mol arepreferred.

Preferred cationic polymers may be: polymers with at least onequaternary ammonium group, a phosphonium group, an acid adduct of aprimary, secondary or tertiary amine group, a polyethyleneimine, apolydiallylamine or a polyallylamine, a polyvinylamine, a dicyandiamidecondensation product, a dicyandiamide-polyamine cocondensation product,a polyamide-formaldehyde condensation product.

Preferred polymers may be those based on a diallyl ammonium compound,particularly preferably those based on a dialkyldiallyl compound whichmay be obtained by a free-radical cyclisation reaction of diallylaminecompounds and exhibit structure 1 or 2. Structures 3 and 4 representcopolymers based on dialkyldiallyl compounds.

In these structures, R₁ and R₂ represent a hydrogen atom, an alkyl groupwith 1 to 4 C atoms, methyl, an ethyl, an n-propyl, an iso-propyl, ann-butyl-, an iso-butyl or a tert.-butyl group, wherein R₁ and R₂ may beidentical or different. A hydrogen atom of the alkyl group mayfurthermore be substituted by a hydroxy group. Y represents afree-radically polymerisable monomer unit, such as for example sulfonyl,acrylamide, methacrylamide, acrylic acid or methacrylic acid. X⁻represents an anion.

A poly(diallyldimethyl ammonium chloride) solution (PDADMAC solution inwater) may be mentioned by way of example.

The aggregate size of the silicon dioxide particles is not limited, butmay preferably be smaller than 0.5 μm. At this size it is, for example,possible to influence the handle and lustre of the textiles.

The pH value of the dispersion may preferably be between 2 and 8.

The dispersion may, for example, be produced as described inEP-A-1013605 or EP-A-1331254.

The dispersion exhibits the advantage over prior art dispersionscontaining silica sols which are either not aggregated or may be presentin partially aggregated form so that less silicon dioxide need be usedin order to bring about, for example, the same slip resistance in thetextiles. Additionally, the aggregate size of the particles and thus thehandle and lustre of the textiles may be adjusted by suitable dispersiontechniques. The advantages are probably attributable to the aggregatedstructure of the pyrogenically produced silicon dioxide powder.

EXAMPLES Cationic Silica-Dispersion According to the Invention (DI)

24.38 g Polyquat 40U05NV (40% PDADMAC solution in water, molecularweight ca 5000 g/mol, Katpol GmbH, Bitterfeld) is dissolved in 800 gdesalinated water. This mixture is gradually incorporated into 600 gsilicon dioxide powder doped with 0.25 wt. % aluminium oxide using adissolver. Sufficient water is then added to achieve a solids content of41%. This is then dispersed for 30 min at 7000 rpm. The pH value of thedispersion is 2.8, the viscosity 28 mPas at 1/s. The zeta potential ismeasured as +42 mV by CVI. The isoelectrical point is at pH 10.1.

Cationic Silica-Dispersion (Reference Dispersion According to the Stateof the Art) (DII)

Durasol®5071, Cognis: 25 wt-% cationic, colloidal silica dispersion.

Foulard-Process: The dispersion DI and DII are contacted with a viscose(Application A1) or a polyester textile (Application A2) using aFoulard-process.

The liquor compositions for Al comprises 100 g/l STABITEX ETR, 6.1 g/lD1 respectively 15 g/l DII, 30 g/l ADASIL SM, 20 g/l ADALIN NI, 20 g/lMgCl₂, 1,0 g/l FORYL 100. The pH of the liquor is <5,5, the liquorpick-up is 100%, the application is dry/wet, temperature for drying is110° C. and condensation takes 3 minutes at 150° C.

STABITEX, DURASOL, ADASIL, ADALIN and FORYL are all trademarks ofCognis.

The liquor composition for A2 is 22 g/l D1 respectively 45 g/l DII. ThepH of the liquor is <5,5, the liquor pick-up is 20%, the application iswet/wet, temperature for drying is 110° C.

In the applications A1 as well as A2 a significant less amount of thedispersion DI compared to state of the art dispersion DII suffice togive the same non-slip effect as measured according DIN 53 934.

1. An aqueous dispersion for use as a finishing agent for textiles,characterised in that the dispersion contains a pyrogenically produced,aggregated silicon dioxide powder and a cationic polymer which issoluble in the dispersion, wherein the cationic polymer is present in aquantity such that the particles of the silicon dioxide powder exhibit apositive zeta potential.
 2. An aqueous dispersion for use as a finishingagent for textiles according to claim 1, characterised in that thepyrogenically produced silicon dioxide powder has a specific surfacearea of 50 to 300 m²/g.
 3. An aqueous dispersion for use as a finishingagent for textiles according to claim 1, characterised in that thepyrogenically produced silicon dioxide powder is doped with up to 1 wt.% of aluminium oxide or potassium.
 4. An aqueous dispersion for use as afinishing agent for textiles according to claim 1, characterised in thatit has a content of silicon dioxide powder of 3 to 50 wt. %.
 5. Anaqueous dispersion for use as a finishing agent for textiles accordingto claim 1, characterised in that the content of cationic polymer isbetween 0.1 wt. % and 15 wt. %, relative to the quantity of cationicpolymer and silicon dioxide powder.
 6. An aqueous dispersion for use asa finishing agent for textiles according to claim 1, characterised inthat the cationic polymer has a molecular weight of less than 100 000g/mol.
 7. An aqueous dispersion for use as a finishing agent fortextiles according to claim 1, characterised in that the cationicpolymer is a polymer with at least one quaternary ammonium group, aphosphonium group, an acid adduct of a primary, secondary or tertiaryamine group, a polyethyleneimine, a polydiallylamine or apolyallylamine, a polyvinylamine, a dicyandiamide condensation product,a dicyandiamide-polyamine cocondensation product, apolyamide-formaldehyde condensation product.
 8. An aqueous dispersionfor use as a finishing agent for textiles according to claim 1,characterised in that the aggregate size in the dispersion is less than0.5 μm.
 9. An aqueous dispersion for use as a finishing agent fortextiles according to claim 1, characterised in that the pH valuethereof is between 2 and 8.